1. Field of the Invention
The present invention relates to a gear assembly and in particular to a gear assembly operable to convert a bidirectional input into a unidirectional output.
2. Description of Related Art
The gearing necessary to transfer the pedaling motion of a rider of a bicycle into the forward motion of that bicycle is well known in the art. Such gearing has spanned from the single ratio, two sprocket system to the more recent complicated ten and fifteen gear derailleur systems used on many current bicycles' gearing assemblies.
Early bicycles typically have a drive system that directly connects the pedals to the rear wheel. Thus, forward pedaling causes the bicycle to move in a forward direction, while rearward pedaling causes the bicycle to move in a rearward or reverse direction. This drive system is unsatisfactory because the bicycle needs to be constantly pedaled in order to continue moving forward. Also, if the rider elects to stop applying pressure to pedal the bicycle, the forward momentum of the bicycle still causes the bicycle to move forward and the pedals to continue rotating. Many bicycles of this type have a braking mechanism in the rear axle bearing assembly such that rotating the pedals in reverse engages the rear brake to stop the rear wheel rotation and the bicycle forward motion.
Newer bicycle gearing systems allow the bicycle rear wheel to continue rotating forward even when the forward sprocket gear and drive chain remain stationary. In such a system, a rider's rotary pedaling motion is transferred from a front sprocket to a rear free wheel sprocket cluster via a chain. The rear free wheel sprocket cluster transfers forward pedal rotation to the rear wheel and allows the rear wheel to rotate forward when the pedals are stationary. Most bicycles of this type have hand brakes that engage pads which apply pressure to the rim of the tire thereby stopping the bicycle. With this type of braking system, rearward pedaling is free-action, neither engaging a braking system nor causing the bike to move in a rearward direction.
Another type of bicycle gearing system described in U.S. Pat. No. 5,435,583 allows a rider to move a bicycle forward by either pedaling forward or by pedaling backward. By allowing the rider to pedal backward and still move the bicycle forward, this system allows the rider to exercise different portions of his/her leg muscles than the portions typically exercised by forward pedaling. The design of the gear system, however, makes it difficult to retrofit the system to an existing bicycle. Further, the gears within the system are prone to break when a high level of power is applied to the pedals.